


This Old Shack

by PineWreaths



Category: Gravity Falls
Genre: Gen
Language: English
Status: Completed
Published: 2015-10-02
Updated: 2015-10-02
Packaged: 2018-04-24 10:14:59
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 4
Words: 9,282
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4915669
Author URL: https://archiveofourown.org/users/PineWreaths/pseuds/PineWreaths
Summary: <blockquote class="userstuff">
              <p>After inheriting the Mystery Shack suddenly, Dipper and Mabel are left trying to figure out what to do and where to go from there, when they find something in the basement below...</p>
            </blockquote>





	1. Chapter 1

“-thank you again for coming on such short notice, Mr. Pines.”

Dipper, snapped out of his daydream for a moment, nodded towards the lawyer with a quiet “Oh, uh yeah, sure.”

The lawyer looked around pointedly, frowning slightly. The chair next to Dipper was empty; His sister’s bus south from Portland to Salem must have been behind schedule, and she’d texted her brother to tell him to insist the lawyer just got on with executing the will, but Mr…. _Gemerland,_  Dipper read off of the little brass name plate, didn’t look like he was the type to be willing to bend rules like that.

There was another ten awkward minutes of Dipper watching the rain patter on the window and Mr. Gemerland did a bit of paperwork and occasionally glanced pointedly at the door; Finally, with a clatter, Mabel knocked on the door, bursting in almost before Gemerland finished saying “Please join us.”

“So sorry I’m late,” she said, red-faced and out of breath. Her hair was soaked, plastered to her lime-green sweater that made her brother smile; Gemerland’s office was varying shades of muted, reserved tans and browns, and her sweater functioned as a sort of black hole, drawing all attention towards it and the little skateboarding kitten on the front.

Apparently Gemerland had noticed, as he gave the innocent fabric kitten a glare that would have ignited paper, and shuffled the papers on his desk before clearing his throat again. “Thank you for joining us, Mrs. Pines,” he said curtly.

She nodded, still wolfing in lungfuls of air as she said “Sorry again about that; There was a jacknifed truck on I-5, and traffic was all kinds of funked up all the way back to-” She stopped speaking and gesturing with her hands as she caught the death glare of the lawyer, and meekly put them back in her lap, shooting her brother a glance and a little smile he returned before the lawyer continued forcefully.

_“In any case,_ we are here to execute the joint will of Mr. Stanford Pines, of Gravity Falls, Oregon, and Mr. Stanley Pines, of numerous locations but most recently also of Gravity Falls, Oregon. I have here their possessions indicated specifically in their wishes,” he said, gesturing to a few cardboard boxes stacked to one side, “With the remainder stored at their residence, the…hm, the  _‘Mystery Shack.’”_  he said with a note of confusion and more than a little annoyance.

Dip shot his sister a little grin, and she’d returned it with the same hint of sadness he knew he displayed as well. They’d gotten the news a few weeks back, about the drifting ship their Grunkles had been sailing; Their health had been failing, and the older Mystery Twins had spent a good chunk of their savings on a small yacht to enjoy together. Dipper was glad that by all accounts they had passed peacefully and together, although for hours after the call he’d been inconsolable.

He knew Mabel had taken it far harder; She had called him four times in the last week, ostensibly to just talk and catch up with “her little brobro,” but Dipper could tell she was hurting. Gabe was as good of a husband as she could have found, but even then Dipper knew that sometimes what you really needed was family to talk to.

He was caught back to attention as Gemerland pulled the first box over. He had a horrible moment of worry that the lawyer was about to open a box full of illegal passports that would create a whole slew of awkward questions to be answered, but instead all that was in it was two articles of clothing: A long, heavy canvas duster, carefully folded, and a slightly faded red fez with the insignia of a hungry fish splayed across it.

He pushed them across the table, the fez to Mabel and the coat to Dipper. She grabbed it, sticking it on her mop of wet brown curls at a jaunty angle, and causing her brother to let out a snort of laughter as he gave her a thumbs-up. “It suits you, Mabes,” he said with a grin; No doubt her kindergarten class would be all over her and her new hat with questions and sticky fingers come Monday.

Dipper then stood, and shrugged on Grunkle Ford’s old coat. It was heavy, the weight of years and travels outside of a mere single dimension giving it impressive heft. He turned slightly, and his sister nodded approvingly.

Dipper was grinning ear-to-ear, mostly because he could feel small various objects in the pockets that he couldn’t wait to be away from the lawyer to examine. Grunkle Ford had made it a habit of slapping away his nephew’s fingers when he tried to see what incredible gizmos were hiding there, and he’d forgotten all about them until he felt the weight of a few of those bump against his leg and chest.

Dipper was reminiscing when  again he perked up after hearing a familiar name, as Gemerland said “-Ramirez, although Mr. Ramirez declined the generous offer so it now falls jointly to you two.”

“Wait, Soos? What did Grunkle Stan give Soos?” Dipper said, confused. Mabel must not have been paying close attention either, as she turned and leaned in as the lawyer sighed and repeated himself. “Mr. Jesus Ramirez declined the key, saying he was currently busy with his tourist attraction in northern Washington, and he insisted that, quote ‘the kids was always closest to Mr. Pines, so they should be the ones to get it.’”

Dipper was still catching up, even as Mabel’s face split into an incredulous and excited grin. “Wait, _what_ key?”

Mr. Gemerland pushed a small, unassuming key ring across the desk. “The key to the ‘Mystery Shack,’” he said, and Dip could almost imagine him giving the air quotes to the name. “The property now belongs to you two, to do with as you please.”

 

 

It was actually several weeks more before Dipper and Mabel could arrange their schedules to meet at the Shack; He had assured his bosses that he would swing by their new office in Vancouver, and double-check that the servers were running smoothly. It was honestly a job he could have done from his desk in Palo Alto, but he had a stellar work record so far so his supervisor had agreed, wishing him a good trip as he left.

Meanwhile, Mabel didn’t have time until school let out for the summer.  _Heh,_ he chuckled to himself as the bus rumbled through the trees, _‘Coming up to Gravity Falls for the summer.’ Just like old times, almost._

He was dropped off at the bus stop on the edge of town, and hoofed the rest of the way in. In many ways, nearly two decades had left Gravity Falls almost unchanged. Bud Gleeful’s dealership had been replaced by a grocery store, and there were a few new housing divisions, but for the most part it felt like he’d never left.

He made his way up the muddy road to the Shack, past the numerous belligerent  _“We’re not open yet, so go away!”_  and _“No trespassing, numbskull!”_ signs before getting to the porch. The signs had mold overgrowing the edges, and months of neglect showed in the tall grasses in the parking lot and around the edges of the wooden porch.

He stood there for a moment, a sense of weight in his chest at the utter stillness. Looking around at the surrounding stand of trees, he could almost see his sister and him playing and running back during that first summer, fighting monsters and investigating.

The warm daydream of playful days long past faded to the grey of the drizzly morning, and sighing, Dipper stuck in the key, unlocking the door and budging it with his shoulder where it stuck in the damp.

Inside, the light from the open door caught motes of dust, and he stifled a sneeze. His Grunkles had been gone sailing for almost a year before they passed, and the Shack had been left unoccupied.

_Well, not completely unoccupied,_  he thought, smiling at the little set of squirrel prints through the dust to one side. Still, he winced slightly, realizing that it probably meant he and his sister would need to clean and shoo all the various critters out of the house during the cleanup.

_Speak of the devil._  He grinned, turning to step out of the door as the rumble of an engine and the crunch of gravel under tires heralded his sister’s arrival. She jumped out, her sweater today a more simple blue affair with a splashing whale on the back. She still made her own sweaters, and time had done little to dilute her enthusiasm for the entire spectrum of the rainbow.

He waved, getting a “Hiya Dip!” yelled back as she turned and began to pull out a suitcase from the back of her car. Gabe parked the car in idle, stepping out to kiss her goodbye after helping her get her luggage to the porch step.

Dipper looked away, hand rubbing his neck awkwardly as he felt a pang of jealousy. He and Izzy had a rough patch a few days ago, and while Dip was sure she’d come around, it meant that his going away party was an aggravated stare as he handed Captain Squishbean, his overweight grey tomcat, to his neighbor to care for while he was away. Overall, Dip would certainly have preferred a kiss and a hug from his girlfriend rather than unspoken threats to his furniture from his furry roommate.

Gabe gave Mabel a final peck on the cheek and then jogged back to the car, pulling away with a final wave out the window. Mabel stood there for a moment, smiling and watching him go as she said sadly “He had a business meeting early tomorrow to lead into some big planning project, otherwise he would have stayed a couple days to help us out.”

She turned, shrugging and then grabbing her brother in a hug. He smiled, and he could feel her hug go from enthusiasm to sisterly affection. She let go, looking at him and then to the house, and in a wistful voice saying “I’m-I’m gonna miss them.”

Dipper followed her gaze, into the kitchen where Grunkle Ford’s miracle lightbulb still hung, and he could almost hear  _“Who wants Staaancaaakes?”_ as his other Grunkle served up a steaming breakfast, the twins having maple syrup races when Ford wasn’t watching and reprimanding them for wasting food.

He hugged her around the shoulder, saying “Me too, sis. Me too.”

They stood there for a moment, looking into the empty house, before Mabel suddenly darted out from under his arm and towards the stairs. “Dibs on the upstairs!” she shouted, and Dipper took a protesting step forward, his arm outstretched as he said “Hey, wait, no fai-”

He stopped, laughing as she cackled triumphantly from the upper bedroom, and grabbed his duffel bag to head into Stan’s old room. He felt a bit of a lump in his throat as he looked at the picture of Stan and Ford on the mantlepiece, their faces hardly older than Dipper and Mabel.

_Hard to believe it’s been this long,_  he thought as he ran his fingers along the dusty glass,  _But there’s finally Mystery Twins in the Mystery Shack again._

Hours later, once he was sure Mabel had gone to bed, Dipper had cautiously gotten up, creeping to the locked-up gift shop and carefully avoiding all the creaky floorboards he could remember. He tensed when one squeaked particularly loudly, waiting with held breath until he was sure he could hear another of Mabel’s snores through the floor, and continued to the vending machine. Carefully, he punched in a sequence that by now seemed like an old friend, and it swung open with a slight squeak of ungreased hinges.

Dipper felt in the coat pocket of the duster, pulling out the journal reverently. He smiled, rubbing the dust off of the golden six-fingered hand marked with a black-ink ‘6,’ before slipping it back into the voluminous pocket. He looked around, and then ducked behind the vending machine, closing it softly behind him.


	2. Chapter 2

The repairs and cleaning went quickly, with the twins managing to clear out the nest of opossums from the pantry and dusting off most of the rooms and floors. They hadn’t managed to thoroughly clean much, if any, of the attractions and oddities in the tourist area; Mabel had tried to sweep one section, and when the duster hit the horns of the beavalope ( _“Half beaver, half jackalope,”_  read the sign on the hot-glued taxidermy hybrid), one had snapped off. leaving Mabel swearing and pulling a little vial of superglue from her purse to repair it.

Here and there, signs of Grunkle Ford’s more scientific and evidence-based displays crept in, with a dollhouse made to-scale by the gnomes as a peace offering when Ford caught them trying to make off with her the second time, and a winking green fire in a small pot that most tourists assumed was artificially colored. Mabel knew otherwise, though; Her and Ford had been the ones who received it as a gift for helping the passing elemental, while Dipper was busy with Stan and an outbreak of poisonous unicorn lice in the gift shop.

She sighed, smiling at the memories as she went back to cleaning. Dipper came through, a double-armful of knicknacks in tow as he dropped them onto the kitchen table to sort through. The week they had to fix the Shack had blown past, and it was already Saturday; Gabe was picking her up tomorrow afternoon, for a red-eye drive home.

Her original plan was to stay for two weeks, but the elementary school administration had called a special session meeting about something or other Mabel could care less about. Still, it meant she had to be there bright and early Monday, and the twins were not  _quite_ done with the repairs.

She looked up at her brother, who was engrossed in sorting out which bird mannequins appeared to be clad in natural plumage, and which ones had been somewhat-artfully spray painted by Stan and Soos decades earlier. Her brow was wrinkled in worry; He had been sneaking around her, occasionally ducking away for far longer than would be needed to run the errands he said he was running, and she could hear him getting up at night and shifting around.

Last night, her curiosity got the better of her, and she had gotten up to see what he was doing, only to find the shack empty but all the doors and windows locked tightly shut. As she had approached the gift shop, she heard the familiar quiet squeaking creak of the vending machine as it swung open, and Dipper’s footsteps coming up from the hidden staircase.

Mabel had managed to hide behind the creepily-accurate wax statue of Grunkle Stan; Evidently he’d repaired the old one at some point, and the bulk concealed her as her brother headed back to bed. She only got a glimpse of him as he passed, but she saw an unfaded, almost-new journal bearing Grunkle Ford’s six-fingered golden-handed sigil and an unmistakeable ‘6’ on the cover.

That had almost caused her to gasp aloud, a hand on her mouth stifling the sound so as not to alert Dipper. _I thought there had only been the three,_ she recalled, as worrying possibilities as to her brother’s nighttime whereabouts began to surface and coalesce. _If the portal that could have destroyed the planet was in the first three…what the heck is in the others?_

She hadn’t dared check down there herself yet; Dawn was just a few hours off, and that didn’t leave enough time for her to wait until her brother fell back asleep. In either case, she was also nearing the limits of her wakefulness,and had retired to bed while vowing to investigate the following night before Dipper got up.

Dipper looked up, giving her a rueful chuckle as he held up a bright pink crow, glitter frosting the wing tips. Mabel laughed as she recognized her own handiwork, and as her brother went back to sorting, her grin faded with worry.

_Dip, please don’t be up to what I think you’re up to._

That night, Mabel laid in bed, her ears burning as she listened for her brother shuffling around before retiring to his own quarters. Finally, he went still, and she waited as long as she dared before inching up. She crept over and past the creaky bits of the stairs and floors; Their last few days here had helped refresh her memory of which parts made the most noise, and she threaded her way to the gift shop with minimal squeaking.

Heart pounding, Mabel keyed in the sequence on the vending machine, letting out a held breath as it beeped and opened to admit her inside. She nearly ran down the stairs, flying to the elevator, foot tapping anxiously as she rode downwards, before it beeped open with a hiss of air.

The control room was lit, various components filling the open workbench areas, but over near the primary controls there was an open ruled notebook filled with diagrams and scribbles. She flipped over to check the cover, smiling slightly as she saw the outline of the constellation of Ursa Major on the cover in gold sharpie.

She had been the one who had suggested that he start his own journals, after they found out about Grunkle Ford, but Dipper had deflected the idea, saying  _“Maybe eventually, but for right now we can talk with Ford directly, ask the author of the journals whatever we want!”_

 _Well, it looks like you started your own anyhow,_  she said with her smile turning to a grimace. Her finger marking the open page, she flipped through the rest of the notebook; Fully half of it was filled with her brother’s messy handwriting and scribbled notes, and she caught snippets of  _“-although the stresses involved would be astronomical as before, they should be able to be contained by Ford’s theoretical-”_ and  _“-unknown until the missing journals are located. Until then, assume the worst and triple-reinforce the phase-.”_

She sat back, stunned; There was  _months_  of notes here, not just what she would imagine the week they’d been here would have yielded. Her mind flew back to Dipper trying on Grunkle Ford’s old coat, and how he’d been giddy, beyond what she’d even expected for a combination of fanboyism and familial respect.  _So Ford left the journal in his coat? Did he intend for Dipper to get it, or did he forget it when they left on the trip?_

Her thoughts came crashing down in a blind panic as the elevator  _ding_ ed behind her, and slapping the notebook back down, she spun to face Dipper as he strode out of the elevator.

 

 

He stopped mid-stride, his expression of silent calculation shifting to confusion and then the fear of a cornered animal, as he glanced around the control room like he expected to find a way out.

Mabel just stood there, arms crossed, and swallowed her building worry and concern.  _There’ll be time for huggy-talky feelings later. For now, let’s grill Dip for some answers._

Summoning a cold steel tone to her voice, she said into the sudden silence “Care to explain exactly _what the hell_  all this is about?”

Dipper stopped looking around, straightening and avoiding her eyes as he rubbed behind his neck. She could see him thinking, coming up with and discarding responses, before he finally sighed, bowing his head before looking up at her, defeated.

In a small, hesitant voice he mumbled “Iwasgonnafinishtheportal,” giving her a sheepish grin at the end of the word jumble.

Mabel caught what he said, but with the same chiding voice said “Couldn’t hear you. Speak up, clearer this time; What is all  _this_ about?”

He groaned, gesturing futilely with his hands as he said in a huff “I was going to finish the portal, finish the repairs Ford was making to it.” He looked at her with a look of mostly-determination, but more than a little embarrassment as well.

Mabel felt her eyes narrow, but her shoulders slouched as she strode over to her twin. He closed his eyes and flinched for the shoulder punch, but then cracked open an eye as nothing happened.

Mabel was standing, shoulders shaking with a combination of anger and worry, one arm held straight down while the other gestured around them. “Dipper, don’t you remember what happened with Grunkle Stan and Grunkle Ford when they built it the first time? It tore them apart! Literally! For _thirty years,_ Dip!”

She stopped, her tone lowering to one of concern as she said quietly “Did you ever stop and think of what that would be like if it happened to  _us_ , brobro?”

He looked like he wanted to say something, but mostly he just looked like she’d punched him in the heart instead of the shoulder. He opened his mouth, but shut it as she continued with a stream of questions.

“Why on earth did you think this would be a good idea? How long have you known about all this; Since you got the coat? Have you been working on this thing  _every night_  we’ve been at the Shack?”

He looked up from his feet at the last question, and with a halfhearted shrug said “Actually, I’ve mostly been taking notes. From what I can tell, it’s basically finished, and there’s just a few damaged parts that needed repairs in order to-”

 _“Dip!”_  she said, grabbing his shoulders and giving them a shake as she looked into his eyes. She was shocked to see tears in his eyes, mirroring her own as she said “Brobro, whatever you’ve read, no weird monsters or aliens or  _whatever_ is worth getting sucked away for the rest of your life!”

“What about for our Grunkles?” he said in a hushed voice, looking at her as he bit the edge of his lip with worry.

 

Mabel stopped, cocking her head, before saying sadly “Oh, Dipper, Ford and Stan are proud of us even if we don’t finish their research…project…portal…thingy.” She finished uncertainly, waving a hand awkwardly in the vicinity of the room, but stopped when Dipper pushed past her to grab his notebook. He came back over to his confused sister, flipping through the entries to one near the front.

Pulling out a set of printouts of some sort, he showed her a graph of some kind, a wiggly noisy line in the middle. Mabel squinted, and gave him a confused shrug.In a voice she could tell he was struggling to keep level and slow, he explained “I…I had a hunch, based off of Ford’s notes here in the latest journal. They filled in some weird gaps from the third journal, gaps I didn’t even realize were there until I knew what to look for,” he said, glancing back to where the three original journals stood side by side in the bookshelf beside the control panel.

He stabbed a finger to the wiggly line. “This is a set of different soil samples, from the Pioneer Cemetery.” Mabel looked up sharply at the name as her brother continued. “I took some samples from all over the park, and brought them to Derek, my old roommate from OSU. He’s running one of their radiology labs now, and was willing to do a spectrum reading for me.”

Dipper then flipped to the second set of graphs. Here, another little bumpy line was visible near the bottom of the graph, but spiking far above it were two sets of twin peaks, the lines looking like little blue mountains surrounded by red wiggly forests. Mabel felt a wave of dawning confusion and horror rising, as her mind raced ahead of her brother’s words.

“These readings are from our-our Grunkle’s graveplots,” he said, his voice faltering for a moment. “Mabes, they’re way above the background radiation for the rest of the cemetery,” he said, a finger tracing the low wiggly red line below the blue spikes. “Hell, Derek said he’d never seen readings like this before,  _anywhere.”_

Mabel turned to him, her head shaking as she tried to think of a rational reason, but everything kept pointing towards Dipper’s findings being real and accurate. “They-they were found on the boat, and a doctor did an au-au-autopsy,” she said, her voice cracking slightly as she could feel herself start to hyperventilate a bit.

“Sis,” he said gently, “We’ve seen monsters that can control bodies and look like anyone. Whatever was buried there was  _not_  our Grunkles, and they  _need_  our help.”

His certainty caused her to turn to look at him, and he nodded, tight-lipped, towards the direction of the portal’s cavern. She hadn’t looked out there yet, and the lights were off, but Dipper stepped over and hit a bank of switches, crackling them on as Mabel stepped through the doorway.

The portal’s frame was still there, looming like the first time they saw it. The columns of light were occluded, their space filled with towering structures of piping and wiring, but the light from the center of the room itself was steady, even instead of the flaring pulses from when Ford had first emerged.

_Wait, light from the-Oh no…_

She turned back towards Dipper, screaming over the sudden whistling of wind in the underground room “What are you  _doing?”_  as she flung her hands up in frustration. Behind her, the portal crackled open, sounding like like a single nail being dragged quickly down a chalkboard.

Dipper stared past her, pointing towards the floor in front of the portal. Mabel turned, and looking for a moment, felt her knees falter. When she had last seen this room, during one of their last visits to Gravity Falls before college, the floor had been a roughly even and smooth dusty scree.

Now, there were large indents, signs of a struggle, and- _Blood_ , she realized, seeing the red splashes dried in the dust. Her gaze followed the signs of disturbance, which led to-

 

Two sets of intermittent clawed fingermarks in the gravel, one with five furrows and the other with six, leading towards the mouth of the humming portal.

 

Dipper had emerged from the control room, walking up and shouting to make himself heard over the howling of the wind. He had a backpack slung over one arm, and his face held both eagerness and concern. “Mabel, they  _need_  us!”

She looked around, now feeling like she was the one trapped. She wanted to help her Grunkles, of course she did, but she had all the obligations of this dimension to deal with. Gabe, for one, would be worried sick if she up and disappeared.

Mabel shook her head wretchedly. “Dip, I  _can’t._ Not right now; I need more  _time_  to-to-to get ready to do  _this,_ ” she said, gesturing again towards the now-howling portal.

Dipper looked crestfallen, but she could see him nod. He looked up at her, giving her a halfhearted smile as he said “I-”

There was an awful _twang,_  and both twins snapped their heads up. One of the immense thumb-thick cables leading to the closest mechanical tower had apparently been too close to the portal, and the plug on one end had popped out and vanished through the portal. Mabel had just enough time to trace the rapidly-spooling remainder of the cable and make a futile lunge, when the loop Dipper had been standing in pulled taut.

With a girlish scream, Dipper was yanked off his feet, his backpack dropping near his sister as he flailed. He managed to grab the edge of a pipe, but as Mabel ran towards him, his grip slipped, and he was sucked backwards. She caught a final glimpse of his form, outlined dark against the blue light, his face open and screaming for her, before he vanished.

 

The other side of the rogue cord detached, whipping past Mabel and thwacking painfully against her hand as she tried to grab it, before it too vanished inside the blue light. The glow began to dwindle, and a mechanical lightly-female voice stated  _“Portal unstable. Collapse imminent. Estimated ten seconds remaining….nine seconds remaining…”_

Mabel looked around, her thoughts and worries and concerns melting away to crystallize into one goal:  _Get my brother back._

She sprinted for the control room, grabbing Dipper’s notebook and turning as she tucked it under one arm. She was almost out the door when she spotted something, dusty and lying to one side near a pile of debris. “Well hello there, old friend,” she almost purred as she grabbed it. Running back to the portal, she grabbed Dipper’s backpack, and with a final look back at the illuminated cavern, she stepped to the edge of the glowing disc.

 _Gabe, be safe,_ she thought, tears at the edges of her vision even as her hand tightened around the strap of the backpack and the dusty butt of her old faithful grappling hook.  _I’ll be back soon, I promise, but first I need to save my little brother._

Then Mabel turned, and stepped through the portal. A second later, it vanished with a crackling flash, and the old cavern was again filled with inky darkness.


	3. Chapter 3

The cold flakes of snow hissed in the fire, sizzling and disappearing in a rhythmic staccato that had started to lull Dipper to sleep for yet another restless night, when he heard a screaming coming from the sky above.

In a heartbeat he was on his feet, the crude blanket lying to slump against the pile of rocks he had his back against. He grabbed his spear, flipping the fabric-wrapped grip to slap against his palm, and he sprinted towards the blue glow.

As he ran, he kicked himself mentally. Dipper had dismissed the possibility of rescue, as he saw the portal start to falter a week ago. He’d been underneath the glow for the first two days, attempting to climb the dangling power cable, trying to shrug off the occasionally ugly jolts he got as the worn wiring arced onto an unprotected hand or foot.

The cable had only been there for so long, though; Dipper figured that since it slumped from the portal to land in a coiled heap a day after Dipper fell, or at least as best as he could estimate from the motley collection of burning stars overhead that granted more or less light at seemingly regular intervals.

 _Stupid_ , he thought, as he sprinted towards the clearing in the grey rocks and desolate red scrub brush. _When has Mabes ever let you down before?_

He stopped short as he saw a slumped form below. Overhead, the shimmering blue of the midair portal had shrunk to only slightly larger than a manhole cover, illuminating his still sister.

 

 

Then she rolled over, groaning, and Dipper let out his apprehensive breath, running over to her to grab her in a bear hug and hoist her onto her feet in excitement. She stiffened, starting to recoil when she recognized his coat and his presence, and hugged him back.

Mabel started crying, big gulping happy sobs as she broke the embrace, giving him a reprimanding punch on the shoulder as she said thickly “Doofus, be  _careful;_  For all I knew, you were d-d-dea-”

He smiled and hugged her again, cutting off her words as she let out a happy blubber. Mabel stepped back, fishing around in her pockets before extracting a handful of crayons and a wad of wax-stained kleenex. She blew her nose, the sound echoing off of the rocky walls around them, and Dipper abruptly remembered several very close calls he’d had in his short visit so far.

“Come on; It’s not safe here,” he said, grabbing his sister’s hand and tugging her off back to where he’d made his camp for the night.

As they walked, Mabel kept staring at him, and after the third time or so that he caught her staring at his face, he stopped and turned to face her.

 _“What,_  Mabel?” he said in an unconvinced tone, as she tried and failed to feign ignorance to his question. Finally she broke down, pointing with wonderment.

“Dipper, you’re-you’re _older…”_ she said, and Dipper turned to look at her, his hand flying to his face in a panic.

_It only felt like a few days, maybe a week or two at most; I’ve only had to sleep a few times, and I’ve eaten four-no, five times, right? But, shit, what if this dimension prolongs the time you can go before that kind of thing becomes noticeable? Has it been years? Decades, already?_

His mind was whirling in a merry panic, before the train of thought abruptly jumped the rails and landed in a burning gorge of confusion as his sister poked his cheek, running a finger across his ragged stubble before she looked at him with concern.

“Dip, I came after you just a few seconds later,” she said in a hushed tone, and he nodded solemnly. _Oh boy, here it comes._

“But, I mean, look at that. You must have been gone a week, heck, two weeks, judging from how long it takes you to get the Indiana Jones fuzz effect going.”

 _Wait, what?_  Dipper echoed his thoughts aloud, his brow wrinkling as he turned to Mabel, her gaze still fixed in amazement on his chin. Without looking up, she said “Like, does it feel all alien-y and stuff, like it grew too fast and is gonna come alive or something?”

Dipper sputtered, waving her away as he sat against a crimson stump of wood stained with fluorescent blue whorls. He continued to fume wordlessly, gesturing to himself before turning to look at her, raising his arms up in annoyance.

“Mabel, you said I looked _old!”_  he finally managed to spit out.

Mabel cocked her head, and in a confused voice tinged with an edge of worry at his antics, she said “Yeah? Well, you  _are_  older. Certainly a couple days judging from the chin thunder you’ve sprouted.”

Dipper tried fruitlessly to hide the abrupt blush, as he’d been  _proud_  of his attempts to grow something that looked vaguely like a goatee, albeit if you squinted at it after multiple stiff drinks.

In a hurt tone, he muttered “Yeah, but, you know…you sounded like I was  _really_  older. Grunkle Ford had talked about how multidimensional travel could do weird stuff with time, and I…I thought…”

His sister nodded, slower this time and with an  _“Ohh”_  of understanding. She sat next to him, wrapping an arm around his shoulders, and said “Sorry. I guess there’s not been a lot of mirrors to examine yourself in around here, huh?” She looked around at the wasteland surroundings, little beyond bare rock, unhealthy grass, and an occasional scattered set of lone trees or huddling brush to be seen.

Dipper’s back stiffened, and he said quietly “Well, you’d be surprised.” He grabbed his sister’s hand, and led her to his campsite. Dip bundled up his blanket, sliding the roll through the makeshift straps on his crude satchel; The old cable had combined nicely with what little he remembered from a weaving class Mabel drug him and Stan off to one weekend, and he had a loose gridded bag with a few rusted cans of food and a metal lighter inside.

_Well, and the picture, but I can show her that later. First, I need to show her ‘where’ we are._

He led his sister onwards through the dirt, and they quickly reached the edge of a cliff he’d been looking for. A thin set of switchbacks ran through the cracked, gravelly soil, but for now he just stood and pointed with the crude spear to the valley below them.

Mabel gasped; Below them the valley had far more trees, although still sparse and few between enough that it toyed with the minimum requirements to be considered a “forest.” Directly beneath them, a small glade opened to reveal first the tip of a lightly-pulsing radio aerial, and next to that a wooden building, bearing an uncanny resemblance to-

“The Mystery Shack, _here?”_  she said, and Dipper nodded. It wasn’t identical, per se, as it lacked all of Grunkle Stan’s signs, and certain angles and material choices made it apparent that someone had likely made this to resemble the Shack.

They’d succeeded; Dipper had barged inside when he had first arrived, expecting to find his Grunkles or at least something familiar in this godawful mess, and  _that_ hadn’t gone well at all.

He stepped over to his sister, laying a pre-emptive hand of comfort on her shoulder. Dipper hadn’t taken the rest of the view as hard as he knew his sister would but it had come as a shock nonetheless. She looked up, seeing the constellation of what served as a sort of sun lighting up the cracked cliffs, the overhanging enormous ledges a signature of Gravity Falls, and nowhere else. But where the town should have been, there was nothing but a huge, blackened crater, the edges ragged and charred.

To Dipper’s surprise, Mabel just let out a little shaky “I vote we get out of here ASAP, brobro. This…this doesn’t seem like a good spot to linger too long.”

Dipper nodded, and started to go in the opposite direction, when Mabel stepped onto the top of the switchbacks. He spun around, and with a voice dripping with nonchalance said “Oh, uh, I don’t-heh, I don’t think we should go poking around down there.”

His nervous chuckle ruined whatever credibility she had decided to fake on his behalf, and she pointed towards his satchel, saying “You were there at least once already, so how bad can it be?”

Dipper started, a sudden cold sweat running down his back, and he stammered in an attempt to find an excuse, his mind racing but focusing again on that damned picture in his satchel, the satchel his twin was pointing to.

He looked down, and breathed a sigh of relief; The frame was completely hidden, behind the blanket and the cans of food;  _She must have just seen the other supplies,_  he thought with a relaxing breath hissing through his teeth to try and quietly calm his frayed nerves.

Dipper let out a nervous laugh, rubbing his neck as he said “Well, I suppose we could check it out, but I really think it’s better if we-”

He had to run to catch up, yelling “Mabel, _don’t,_  what if there’s-” after her, as she giggled and ran as fast as she dared down the switchbacks.

 

 

They reached the bottom unexpectedly quickly, and Mabel screeched to a halt as Dipper nearly ran into her back. His grip on the spear was white-knuckle, and like that time before, the slow rising wind seemed to make the building creak, as if it was breathing.

She didn’t seem to mind, taking a step forward before Dipper’s hand in front of her stopped her. He was watching the quietly-shifting building like a hawk, and in a quiet voice said “Alright, a few things before we go in. One, you have to be as quiet as possible. That is not  _our_  Mystery Shack, and it’s not empty. Two, we have to be quick. I nearly was killed last time,” he said, ignoring her spin to look at his face with motherly worry, “And I’d fancy not repeating the danger.”

Then, a light flicked on in the house, and a distant grumbling voice could be heard. It was familiar, newer to the twins than his brother but still as familiar now as a pair of old shoes. The light was occluded, and the shape of their Grunkle was cast against the drawn blinds, as the distant voice continued almost inaudibly.

Mabel turned excitedly towards Dipper, but he quickly jammed his hand over her open about-to-speak mouth. Her expression shifted from hurt to confusion, but  widened as her brother spoke, trying to keep the tremor from his voice.

“Third, and most important: That is  _not_  Stanford Pines.”


	4. Chapter 4

Mabel just looked at Dipper in worry. “What do you mean that’s not Grunkle Ford? It looks like him, sounds like him, and he’s  _missing._  How are you so-”

Dipper cut her off with a shake of his head. “It’s…some kind of construct, that Ford made or was made _from_ Ford. From what I can tell it’s got some of his memories judging from how it spoke, but for the most part it just guards the weird not-Shack.”

His brow furrowed. “Plus, it’s younger than the Ford we’ve seen, so even though he knew-knows us today, this version I think might have been made before he escaped the portal.”

He looked up at the squat, reddish-brown almost-wood that was carved to look like uncomfortably-familiar corners and edges of the Shack, the facsimile hunched between a set of dirty, leafless grey-and-brown treetrunks. The imposter building almost taunted Dipper, and if not for his previous warding experience he’d probably be charging in there again right now.

He sighed, as Mabel continued to look over the Shack. “Mabes, it’s  _really_ not safe for us to go looking around there,” he hissed, tenderly feeling the bruises he’d gotten last time. “Besides,” he continued, looking back towards the Shack, “There are too few entrances. Not-Ford will be able to catch us no matter how we try and sneak in.”

His sister sat back, holding her chin and musing, before she said quietly “I think I have an idea. Dipper, if you were an extradimensional demon, how would you try and get inside?”

Dipper stopped, frowning as he considered it before shrugging. “I suppose I’d either pull a Big Bad Wolf and break it down, or try and be like Bill and connive my way inside.”

He gave her a rueful smile. “I doubt either of us has the firepower to get past Ford’s replica, and I know I’m certainly not enough of a liar to be able to B.S. my way into the house either.”

She just grinned at him, causing him to look around self-consciously as he muttered “What?”

She punched him in the shoulder. “Brobro, if you had to describe Bill in one word, what would it be?”

Not seeing where she was leading, Dipper shrugged again, saying with a bit of frustration “I dunno. Jerkish. Annoying. Arrogant.”

She nodded, and nodding her head towards the door, said “Do you think he ever tried knocking?”

 

 

“This idea is bad”

“This idea is  _fine,_  Dipper. Now stop fidgeting and try and look presentable.” Mabel and her brother were standing on the porch, the ringing of the house buzzer fading as a clumping set of footsteps came to the door.

The heavy oak door flew open, and carrying a rifle the size of Dipper, Ford’s impersonator looked at them, pivoting the rifle between them as Mabel smiled sweetly and Dipper attempted to summon as much of a smile as he could muster given the circumstances.

The figure lifted the rifle, the motion sending a flicker through the hologram. Dipper had seen the shimmer earlier when he fled the Shack the first time, but was still glad to see his memory was accurate instead of getting a hole blown in him by a laser cannon.

“Hello, Grunkle Ford!” Mabel said sweetly, but Dipper could tell she was enunciating clearly like he had recommended. He had also said that he would keep quiet as much as possible, in case his startled shrieks from earlier had primed some additional defenses against him entering.

The hologram scanned Mabel, a horizontal blue beam of light sweeping over her as Ford’s puzzled voice said in a slightly-halting voice  _“DNA match of 99.975% +/- 0.01% confirmed.”_

His normal tone resuming, he made the eerily familiar motion Dipper had seen before as he rubbed the back of his neck, muttering “I, uh, I didn’t know I had grandkids.” Mabel opened her mouth to correct him, but Dipper elbowed her and shook his head silently as the hard-light construct stepped inside.

In between shimmers, Dipper could make out a robotic skeleton, looking like it was cobbled together from spare parts, but he swallowed as he saw that the large gun it carried was entirely real. It strode past them, leaving them in the misshapen room where the kitchen would have been, and entered the living room instead. The fish tank, TV, dinosaur skull; Everything was gone, replaced by an odd lit-up harness that the fascimile-Ford seemed to gently fall forward into.

The shimmering hologram became far more inconsistent, large patches appearing and vanishing at random as computing power was diverted elsewhere. Dipper sidled up to his sister, who had just come down from what passed as the stairs, shaking her head in confusion. “Our attic’s got a few boxes in it, but nothing important. I got a can of beans, but for all I know this could have been here for almost half a century.”

Dipper shrugged, his mind elsewhere as he murmured urgently “Ok, the Ford-bot is recharging, or something. I think it might be using one of those neural networks Grunkle Ford told me about once; They’re not as fast as human brains, and the main processor is pretty bulky, but overall they are still just as smart as you or me if you give them time.”

He sighed, his hand balling into a fist as he distantly wished he’d kept his spear handy. “I don’t think we can destroy it before it fries us, so we need to figure out what it’s guarding, what Ford wanted protected here so badly, and fast.”

She nodded, and they both looked towards the hole in the wall where the vending machine door would have been. “Well, why go to the effort to include a basement if you don’t put anything in it,” Dip murmured, and Mabel led the way down the misshapen stairs.

The convenient elevator had been replaced by another ramshackle set of stairs, and they followed it to the bottom, Dipper noting with dry interest that the middle floor where the study had been was left blank, and that their Grunkle had instead hung a mirror there at some point. Dipper’s eyes widened as he saw his disheveled expression, saw the short shock of of a beard, and then he wrenched himself away and followed his twin down to the very bottom.

As Mabel pushed open the thin wooden door, cracks in the ceiling of the enormous cavern illuminated the scene. There was a huge triangular portal, the dead metal glinting dully, and Dipper could make out twin obelisks of machinery like the ones he’d worked on in their own dimension, under their own Shack. These ones were in a far earlier stage of development, but the resemblance was striking nonetheless.

“All right, spread out Mabes. I think Ford hid one of the Journals down here, or something as important as one.” He stepped over to the desk, opening drawers and moving stacks of scribbled-on paper to try and find anything useful.

Behind him, Mabel had begun to pull the tarp off of a piece of equipment, when she stepped back with a gasp. Instantly, Dipper was up and alter, looking towards the empty doorway before he caught sight of what she saw as well.

 

The device was squat, looking like an old computer rimmed with rusting scrap iron. Suspended in front of the monitor was a pair of prongs, the gap in between them empty, but conforming to the exact shape the rest of it suggested from his own recollection. It was evidently a memory-tube reader, just like the one he and his sister had encountered all those years ago when they’d stumbled upon the existence of the Society of the Blind Eye.

Lying next to it, the both glass bulbs shattered into uselessness, was a memory-erasing gun, and Dipper could feel an unpleasant suspicion begin to gnaw at the back of his mind.

 

Mabel just looked at him, unsure as she asked him “Wait, was that it? Why would Grunkle Ford want to guard this old junk so badly?”

Dipper just said tersely “We need to keep looking. The Journal  _must_  be around here somewhere.” He strode into the cavern beyond, while Mabel continued to search the false control room.

The cavern was just as ominous now as the “real” version had been, although Dipper felt far more uneasy here; The purple light of what passed for a sun was one reminder, and the fear of a killer robot at any minute was a strong second indicator as well that this was certainly not “home.”

As he poked one of the pylon connections cautiously, Mabel’s voice called his name, and he ran over. She was just looking at where a hole had been carefully bored into the side of the desk. A red symbol was painted on the wood; _It’s the same as Grunkle Stan’s scar,_  Dipper thought with a sad grimace. Reaching in, he plucked out a dust-covered memory tube, and turned it over.

 

 

Written on a single line was the number ‘4’.

 

 

His breath caught, and Dipper carefully tightened his grip, stepping in a straight line to the memory reader. He glanced at Mabel, and she hesitated, biting her lip for a moment before nodding.

“I  _need_  to know too, Dipper.” He nodded slowly, and could feel himself tense as he saw the first images start to flash on the screen, as the prongs clicked into place on either side of the memory tube.

His gaze was unfocused, and he let out a little quiet  _“No…”_  to himself as his twin squeezed his arm. On the screen, was the familiar blue-white blaze of the portal. The ground was the same red stone as above their heads, the purple sunlight looking like it was probably midmorning in the shot.

Visible through the opening of the portal was the head of Fiddleford McGucket, as he looked around in frantic confusion. From off-screen, Grunkle Ford approached, his face looking like he was attending a funeral as he carried a handmade wooden chair alongside him.

His voice sounded tinny through the speakers: _“Stanford! What…How are you here? Wait, are you-Bill, is that you?”_  Grunkle Ford had shaken his head, saying quietly _“No, Fiddleford, it’s me. I’m sorry.”_

_“Sorry for what? Stanford, how did you get here?”_  Stanford just mutters  _“Accident,”_   before meeting McGucket’s gaze.  _“It doesn’t matter now, though, Fiddlesford. Bill is coming any time, and I need to…to tell you something, something important before you go"_

Fiddlesford just frowned in confusion, saying  _“What? Ford, what’s so damned important that it can’t wait-”_

Then he noticed the chair, and as he placed it down and sat in it, Dipper could see Grunkle Ford had the butt of the memory-gun sticking out of the end of it.

His throat tightened as he heard Ford say  _“I…I’m sorry, Fiddles. There’s not a better way I was able to find, in the time I have. I only hope one day you can forgive me.”_

He then began to recite, figures, observations, dimensions and descriptions., in a cold and emotionless even tone. He sometimes slowed, but never stopped and Dipper skipped the playback ahead, his mouth dry. When the playback resumed each time between skips, Fiddleford was alternately pleading or yelling at Ford to release him, to let him get back and escape sooner, but his Grunkle remained stoically silent.

Finally, after what the timestamp on the monitor said had been almost an elapsed day, Ford stepped back, giving a final wave and apology to Fiddleford. 

Then there was a crack of thunder that sounded utterly alien, and the viewscreen darkened into black, red, and orange, as flickering flames momentarily illuminated monsters, and a godawful and familiar laughter emanated from the screen.

Barely-visible in the screen filled with nightmares was Grunkle Ford. He lifted up the memory gun, dialing in a setting carefully, and then fired. The flash of white light caused Fiddleford’s eyes to go wide, and then he slumped forward, partially conscious as Ford began to walk away. 

Mabel had already squeaked in dismay and looked aside, but Dipper took a second too long, and part of the suddenly-illuminated writhing horrific nightmare vision had managed to etch itself onto his mind. He kept his eyes clamped shut as Fiddleford’s screaming emanated out from speakers, and he finally managed to mush the _“Stop”_  playback button. He tore the memory tube out of the holder, gasping for breath as he silently reminded himself: _You got Bill, you guys got him, he can’t hurt anyone anymore. You’re ok, he can’t hurt you anymore._

Mabel looked at him, as he pocketed the memory tube, and managed to get his breathing under control. With a long breath, Dipper said  “So, off to look for the last one?” she said, and he nodded.

“I think we-”he started to say, before a loud thump on the stairs made Dipper turn. His stomach did a little somersault when he remembered  _The defense hologram._

Grinning reassurance towards Mabel, Dipper grabbed a discarded two by four, and hoisted it onto his shoulder.  _Well, with our powers combined, maybe we can get out of here sooner rather than later. If we’re lucky, the portal will even spit us out at the right time too!_

Both twins released their battle cry in unison, as a fusillade of blows and a grappling hook came pouring on the robot as it poked around the corner.

_“Mystery twins!”_

 

 

* * *

 

 

A small warren of rabbits had taken up residence inside of the hollow structure. The spaces were perfect, but after generations of stability and protection, they had to flee as the machinery rumbled to life, and a glowing blue shimmer filled the spherical area in the middle of the device.

Out of it tumbled to sets of twins, bandages crisscrossing them and a general sense of stench and dirt notable. Still, Dipper did a quick headcount and was desperately glad to hear that number match with the appropriate number in his head, and he got to his feet, brushing himself off. Grunkle Stan accepted his offered hand to get to his feet, but Grunkle Ford ignored it, trying and failing to get up until Mabel took pity on him and scooped him up under the arm to right himself,

After everyone had dusted themselves off, Dipper strode into the control room, already breathing out in partial relieve. The existence of it at all had narrowed them down to half of reality, rather than the whole thing.

_Well, no time like the present to find out,_ he thought as he ran up the stairs. The elevator button did nothing, a worrying initial sign, but they followed the service stairs up. Dipper ran to the door, noting where an ivy sprig or two had begun to poke through the floorboards, as the worrying sign became a billboard of anxiety.

Dipper wrenched the door open, brushing aside a few trailing strands of ivy vine, and as one, the four Pines gasped at the scene outside of what had once been the Mystery Shack.

A mixed feeling of apprehension and relief crossed Dipper’s mind as he looked out into the morning air.

_Everything is different now._

 

**FIN.**

**Notes for the Chapter:**

> I'm not super-pleased with how this one turned out, as a lot of my plot for the 4th chapter was contingent on plotpoints that The Last Mabelcorn proved impossible. I may end up revisiting and editing this story at a future point.


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